feat: add built-in typeOf operator to PocomathInstance

src/core/PocomathInstance.mjs

@@ -26,6 +26,7 @@ export default class PocomathInstance {
       'install',
       'installType',
       'name',
+      'typeOf',
       'Types',
       'undefinedTypes'
    ])
@@ -153,7 +154,13 @@ export default class PocomathInstance {
          if (type === 'any' || this._templateParam(type)) continue
          this.installType(type, spec)
       }
-      this._installFunctions(other._imps)
+      const migrateImps = {}
+      for (const operator in other._imps) {
+         if (operator != 'typeOf') { // skip the builtin, we already have it
+            migrateImps[operator] = other._imps[operator]
+         }
+      }
+      this._installFunctions(migrateImps)
    }
 
    /**
@@ -305,6 +312,10 @@ export default class PocomathInstance {
 
       // rebundle anything that uses the new type:
       this._invalidateDependents(':' + type)
+      // update the typeOf function
+      const imp = {}
+      imp[type] = {uses: new Set(), does: () => () => type}
+      this._installFunctions({typeOf: imp})
    }
 
    /* Returns a list of all types that have been mentioned in the